1. Field of the invention
The present invention related to a process for the preparation of high purity carbon monoxide by the decarbonylation of methyl formate.
The conventional process for producing high purity carbon monoxide comprises cracking methanol or the partial oxidation of LPG and naphtha to obtain a mixture of carbon monoxide and hydrogen, which has to be purified through the cryogenic separation or selective adsorption processes. Also known is the partial oxidation of petroleum coke and residual oil.
These conventional processes require complicated equipment and facilities, and have high capital costs. Now high purity carbon monoxide can be easily obtained directly from the catalytic decarbonylation of methyl formate without any purification equipment.
2. Description of the prior arts
The well known prior art process of pyrolysis of methyl formate involves (a) a process wherein a mixture of methyl formate and methanol are pyrolyzed at a temperature of 200.degree.-500.degree. C. in the presence of a catalyst comprising an alkali metal compound (U.S. Pat. No. 4,303,630); (Japan Patent JP56-32,315;JP56-125,212); (b) a process wherein methyl formate is pyrolyzed at a temperature of 50.degree.-200.degree. C. in the presence of a catalyst comprising an amidine or a base and epoxide (U.S. Pat. No. 4,474,744); (c) a process wherein methyl formate is pyrolyzed at a temperature of 200.degree.-550.degree. C. in the presence of active carbon (Japan laid-open Patent 52-36609).
Among the above mentioned processes, process (a) stipulates that the concentration of methyl formate be limited to 10-70 wt %. If the concentration is less than 10 wt %, the yield of carbon monoxide will be decreased. On the other hand, if the concentration is higher than 70 wt %, the amount of hydrogen evolved will be larger and the purity of the carbon monoxide will be decreased. Therefore this process can not produce carbon monoxide of high purity when the methyl formate concentration is higher than 70 wt %.
The process (b) stipulates that the reaction be carried out in a liquid phase, thus requiring an additional catalyst recovery step.
In the case of process (c), a large amount of hydrogen is also produced, thus making it impossible to obtain carbon monoxide of high purity.